Like the others I use Pinnacle - but the principle should be the same and quality should be excellent unless either the settings are askew or you have system limitations.
Does the software give you the option of capturing for eventual writing to DVD? If it knows what you're going to do with it then it will give you the choice of quality relating to that output (there's no point in capturing at DVD best quality if you're going to put it on the internet, for example).
I use a simple firewire card for capture and, like easyrider, there's no perceptible difference in quality (and I've got a 50" telly, so would notice it!).